Abstract for Project-3 Nuclear Rheology & Stability in Cancer The total length of human DNA in each nucleus (~2 meters) multipled by the number of nucleated cells in an adult human (~10 trillion) gives a total length of DNA in each person that would stretch from the Sun to Pluto and back. A lamina of proteins akin to keratins in your fingernails underlies the nuclear envelope and surrounds the chromosomes contained within each nucleus, and while lamin proteins somehow contribute to nuclear shape and DNA stability, roles for lamins in cancer are extremely unclear. This project focuses on nuclear rheology and stability down to the single molecule level, especially in dynamically migrating and invasive cells. Hepatocellular carcinoma (HCC) tumors exhibit atypical nuclei as many cancers do, and initial profiling of HCC suggests significant changes in lamins, which need to be confirmed and understood. We have recently shown that lamin levels can be mechanosensitive in responding to tissue stiffness [Swift Science 2013], which is especially relevant to HCC because the human liver generally stiffens prior to HCC development [Mueller 2010]. We have also recently found in initial studies that at least one lamin isofom can regulate cell migration and survival through constraining pores [Harada J Cell Biol 2014]. Preliminary results further indicate a relation to DNA damage and repair that we seek to clarify mechanistically down to single molecule levels through the expertise of the Greenberg Lab [Shanbhag Cell 2010]. Our Aims to more deeply study lamin effects on nuclear rheology and stability illustrate the potential consequences of liver tumor stiffening studied in Project-1 and the potential downstream mechanosensitive phenotypes for Project-2. Dennis Discher (Eng'g. and Physics): Nucleus, Cell, & Matrix Mechanics in Motility & Cell Fates Roger Greenberg (Cancer Biology): DNA Breaks, Repair, and Epigenetics 1